It’s a very effective hack, but a hack nonetheless unfortunately.
Shift-clicking to add to a temporary buffer is a very neat UX pattern, that reminds me of browser tabs (see Vivaldi browser, for an expansion around that). The current Obsidian implementation is like having a single-tab browser, with the only way to work on several files all at once being bookmarking them (that invalidates the function of bookmarking in the first place).
If nothing comes up, though, starring could definitely be good enough — thanks for the suggestion!